They say there are two kinds of people in the world: those who divide the world into two kinds of people, and those who don’t.

I’m definitely the first kind. My great interest is human nature, and I constantly search for patterns to identify what we do and why we do it.

I’ve spent years studying happiness and habits, and it has become obvious to me that there’s no magic, one-size-fits-all answer for building a happier, healthier, more productive life. Different strategies work for different people—in fact, what works for one person may be the very opposite of what works for someone else. Some people are morning people; some are night people. Some do better when they abstain from a strong temptation; others, when they indulge in moderation. Some people love simplicity; some thrive in abundance.

To help figure out what I was missing, I posed a num­ber of questions to readers of my website, including: “How do you feel about New Year’s resolutions?” “Do you observe traffic regulations—why or why not?” “Would you ever sign up to take a class for fun?” As readers’ responses poured in, I saw that distinct patterns were threaded through the various answers. It was almost weird—as though groups of people had agreed to answer from the same script.

For instance, about New Year’s resolutions, a subset of people gave virtually identical answers: “I’ll keep a resolution if it’s useful, but I won’t start on New Year’s Day, because January 1 is an arbitrary date.” They all used that word: “ar­bitrary.” I was intrigued by this specific word choice, because the arbitrariness of the January 1 date had never bothered me. Yet these people were all giving the same answer—what did they have in common?

And many people answered, “I don’t make New Year’s resolutions anymore because I never manage to keep them—I never make time for myself.”

Another group said, “I never make resolutions because I don’t like to bind myself.”

There was some meaningful design here, I knew it, but I just couldn’t quite see it.

Then finally, after months of reflection, I had my eureka moment. As I sat at my desk in my home office, I happened to glance at my messy handwritten to-do list—and suddenly it hit me. The simple, decisive question was: “How do you respond to expectations?” I’d found it!

I’d discovered the key. I felt the same excitement that Archimedes must have felt when he stepped out of his bath. I was sitting still, but my mind was racing forward with thoughts about expectations. I grasped at that moment that we all face two kinds of expectations:

outer expectations—expectations others place on us, like meeting a work deadline

inner expectations—expectations we place on ourselves, like keeping a New Year’s resolution

And here was my crucial insight: Depending on a per­son’s response to outer and inner expectations, that person falls into one of four distinct types:

Upholders respond readily to both outer expectations and inner expectations

Questioners question all expectations; they meet an expectation only if they believe it’s justified, so in effect they respond only to inner expectations

It was that simple. With just one single, straightforward question, all of humanity sorted itself into these categories.

The Four Tendencies framework clarified the striking patterns of behavior I’d perceived, and I was able to make sense of what everyone else had seen—but no one else had noticed.

When I mapped the complete system on a sheet of paper, in four symmetrical overlapping circles, my framework showed the elegance of a fern frond or a nautilus shell. I truly felt that I’d uncovered a law of nature: human nature. Or maybe I’d created something more like a Muggle Sorting Hat.

The more I’ve studied the Tendencies, the more I’ve come to see their tremendous influence.

When we consider the Four Tendencies, we’re better able to understand ourselves. This self- knowledge is crucial because we can build a happy life only on the foundation of our own nature, our own interests, and our own values.

Just as important, when we consider the Four Tendencies, we’re better able to understand other people. We can live and work more effectively with others when we identify their Tendencies— as coworkers and bosses, teachers and coaches, husbands and wives, parents and children, health-care providers and patients.

Understanding the Four Tendencies gives us a richer understanding of the world.

RELATED CONTENT

It’s not that the spiritual nourishment offered by my youth group and my childhood church wasn’t authentic. It’s just the way in which I participated in it as an introvert wasn’t authentic to me. What was missing all those years was an invitation to the interior journey.

Who hasn’t wished they were more purposefully present for their friends and loved ones? Here, acclaimed author Gretchen Rubin writes on 5 tips to becoming a more thoughtful, attentive, validating listener.